Printable coating

ABSTRACT

A primer-less coating composition for facestock comprises: a binder being a water-dispersible polymer; an ethylenically unsaturated compound which is aqueous-dispersible and miscible with or bonded to said water-dispersible polymer, wherein said ethylenically unsaturated compound is able to form a covalent bond with an ink; and a crosslinker, wherein said crosslinker is suitable for binding the coating to the facestock. The coating composition may be applied to a substrate to form a printable film. A printed film in accordance with the invention may be used in a label, for example for use on a container such as a bottle.

This application is a Continuation Application of U.S. ApplicationSerial No. 13/220,772, filed on Aug. 30, 2011, which is a continuationof U.S. Application Serial No. 13/128,536 filed on Jun. 7, 2011, whichis a National Stage Application of PCT/GB2009/051670 filed on Dec. 8,2009, which claims priority from United Kingdom Patent Application No.0822412.3, filed on Dec. 9, 2008. The entirety of all of theaforementioned applications is incorporated herein by reference.

FIELD

The present invention relates to an improved coating to which print canbe applied. In particular, though not exclusively, the present inventionrelates to an improved printable film having good adhesive propertieswhen used with radiation curable ink.

BACKGROUND

In recent years, diversification of printed products has requiredprinting on a wider variety of materials in sheets; for example, papers,synthetic papers, polymer films such as thermoplastic resin films,metallic foils, metallized sheets, etc. These printed items are printedby methods such as by offset printing, gravure, flexography, screenprocess printing and letterpress printing. In these printing methods, amethod which uses radiation curable ink has recently become popularbecause radiation curable inks cure rapidly, and the printing methodwhich uses radiation curable ink is of superior handling. Radiationcurable inks are known to be useful in the printing of packaging, labelsand non absorbing printing materials. Radiation curable printing inkstypically contain unsaturated acrylates, polyesters, photoinitiators,and additives. In electron beam cured inks however, the photoinitiatorsmay be omitted.

After deposition of the radiation curable ink on the printable item, theprint is exposed to radiation and hardens within a fraction of a second.Printing speeds up to 300 m/min are attained during continuous printing.At present, there is a great demand for sheet-like printable items.

In printing methods, the printing sheet desirably has good sheet runningproperties and anti-blocking properties, producing uniform spread of theink over the surface of the sheet, as well as antistatic properties.Besides these generally required properties, in printing methods whichuse radiation curable ink, the printing sheet requires in particular theproperty of adhering strongly to radiation cured ink.

In particular, radiation curable ink printed polymer films, intended foruse as labels, for example in the bottle labelling market, should beresistant to both freezing water conditions (to allow storage of theresultant product in coolers or ice buckets) and sterilization processesfor example by exposure to steam (to ensure pre-labelled bottles are fitfor filling).

European patent application EP-A1-410051 discloses printing sheetscomprising a support layer and a surface layer on at least one face ofsaid support, said surface layer containing at least an acrylate basedpolymer and an unsaturated compound (cinnamic acid or derivativesthereof). This document does not teach anything about the possibility ofuse of other monomers to replace cinnamic acid.

WO-A-02/048260 discloses what are said to be improved binders,ink-receptive compositions and coated substrates containing a binder, aparticulate filler and a mordant. Preferred binders include one or moreacrylic copolymers made with at least one wet abrasionresistance-enhancing monomer. The coating compositions disclosed thereinare fully saturated, with ink receptivity being provided by the mordantand/or the filler.

WO-A-01/60878 discloses co-mingled polyurethane-polyvinyl estercompositions for use as coatings intended for protectivity rather thanink receptivity. This document suggests the use of a water-dispersibleUV-hybrid coating which is fully cured during the manufacturing process.

US 2002/0098340 discloses a printable film comprising a substrate and atleast a surface layer which covers at least one face of the substrateand which comprises a water dispersible polymer and an ethylenicallyunsaturated compound. However said product can be expensive andcomplicated to produce due to its multi-component nature. This documentteaches the use of primers intermediate between the substrate and thesurface layer to provide a satisfactory level of adherence.

However, the above listed materials formed in sheets, especially polymerfilms, do not sufficiently adhere to radiation curable ink afterprinting and curing, especially in these extreme conditions. Accordinglythe printed and radiation cured ink is problematic in that the printedand radiation cured ink separates from the polymer film.

Improvements are required in the area of printable films, in order toachieve a product which is cost-effective, easy to manufacture, andwhich also has appropriate adhesion properties.

SUMMARY

From a first aspect the present invention provides a primer-less coatingfor facestock, comprising: a binder being a water-dispersible polymer;an ethylenically unsaturated compound which is aqueous-dispersible andmiscible with or bonded to said water-dispersible polymer, wherein saidethylenically unsaturated compound is able to form a covalent bond withan ink; and a crosslinker, wherein said crosslinker is suitable forbinding the coating to the facestock.

Suitable substrates, which can be used in this invention as thefacestock, are polymer films, especially polyolefin films, papers,synthetic papers, woven fabrics, nonwoven fabrics, ceramic sheets,metallic plates, and multilayer composite sheets formed by combinationof said materials. For printable film intended for use as labels,polyolefin films are preferred, especially oriented polypropylene films,and still more preferred is an oriented polypropylene film according toEP-A-0202812.

The printable films referred to herein are films which can be directlyinked, i.e. a film of which the surface layer is strong enough to resistthe pull of the tacky ink, otherwise areas of the surface layer may bepulled away from the surface, giving a defect known as picking.

The coating formulation, resultant coating, and coated products do notcomprise a primer. This gives advantages not only in terms of cost butalso in terms of production equipment and simplicity. Furthermore, theprimer-less systems allow improved printability. The considerable volumeof prior art disclosing primers teaches away from the primer-less systemof the present application.

In some prior art systems an open printable surface is provided by aninteraction between a polymer (for example an acrylic polymer) and anethylenically unsaturated compound (for example EBECRYL® (EthoxylatedTMPTA) from Cytec Industries Inc.). When the film is printed the wet inkadheres to the coated surface and then, when the printed film isradiation-cured, the UV initiators (contained in the ink) start aradical curing reaction which cross-links EBECRYL® with itself and theink and thus binds the ink on the surface of the film. The skilledperson has typically avoided using crosslinkers for the purpose ofbinding the coating to the film, because of the fear of giving rise to ahard, unprintable film; instead a separate primer layer has usually beenused in prior art systems between the film and the coating for thepurpose of binding the film to the coating.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows an example of a coated film in accordance with the presentinvention.

DETAILED DESCRIPTION

Surprisingly the present inventors have found that a crosslinker can beused in the coating formulation in order to effect the binding, withoutcompromising other qualities such as good printability. The presentinventors have found that a crosslinker can be used to bind functionalgroups on the film surface with functional groups in the components ofthe coating composition. The crosslinker also provides the film withwater-resistance without excessively hardening the product, therebymeaning that the surface can still be readily printed. In fact,improvements in printability are seen.

The crosslinker is used such that it can provide effective adhesion (andoptionally also water resistance) whilst also resulting in effectiveprintability. Non-isocyanate crosslinkers are preferred, because theinventors have found that isocyanate can self-crosslink to give a hard,print-resistant, polyurea component. The inventors have obtained goodresults with carbodiimide and especially aziridine crosslinkers andtherefore these crosslinkers are preferred. The skilled person willappreciate that other crosslinkers, which provide the binding effect andresult in effective printability, are also within the scope of thepresent invention.

The system of the present invention can again be contrasted withprimer-based systems of the prior art, wherein a bond is formed by meansof the separate primer layer which is present only at the interfacebetween the film and the topcoat and is not present in the topcoatitself.

In the present invention the cross-linker is typically able to reactwith the ethylenically unsaturated compound, which may or may not formpart of and/or be pendant from, the backbone of the water dispersiblepolymer. Optionally the chemical interaction is a three-way interactionincluding these two materials and also the polymer, thereby effectivelyforming a pre-polymer on the film surface for the reception of ink andsubsequent curing by the radiation cure.

Furthermore, the cross-linker is typically present in the coatingcomposition in an amount in excess of that required for stoichiometriccross-linking of the water-dispersible polymer. This enables there to besome crosslinker left available to react with the ethylenicallyunsaturated compound.

In the primerless system of the present invention, the crosslinker ispreferably present throughout the coating. The crosslinker preferablyreaches from the film (substrate) where it binds to functional groupsthereon (for example, acid, hydroxyl and amino groups thereon), all theway through the topcoat where it crosslinks the polymer and interactschemically with the ethylenically unsaturated compound, to the surfacewhere it locks in the ethylenically unsaturated compound and yet leavesfunctional groups available on the ethylenically unsaturated compound tobind the ink. It is a key feature of the present invention that theethylenically unsaturated compound present in the system retain at leastsome of its unsaturation at the point at which ink is applied to thesystem. In other words, the coating comprises an ethylenicallyunsaturated compound which is not cured to any extent that would fullyremove ethylenic unsaturation from the compound and prevent its bindingto an ink applied to the coating surface. The ethylenically unsaturatedcompound used in the coating formulation of the invention must have thecapacity (through one or more of its ethylenically unsaturated groups)to bind to an ink applied to the coating. In other words, theethylenically unsaturated compound forms a covalent bond with an ink byvirtue of ethylenically unsaturated groups extant in the coating at thetime an ink is applied thereto. A coating formulation originallyformulated with an ethylenically unsaturated compound but then curedprior to inking such that insufficient ethylenically unsaturated groupsfor ink adhesion remain in the coating will not be in accordance withthe invention.

The combination of components is such that excess crosslinker can beused without resulting in over cross-linked, hard unprintable film. Somepreferred crosslinkers are able to avoid the disadvantages of excesscross-linking by hydrolyzing instead. The following can also play arole, and can be varied by the skilled person accordingly: the reactionwith the ethylenically unsaturated compound; the three-way interactiontaking into account the polymer; the particular functionality of thematerials including for example a limited level of acid functionality inthe polymer make-up; the amount of crosslinker; and the monomers chosenwhen performing the original polymerization.

The mechanism of the chemical interaction between the crosslinker andthe ethylenically unsaturated compound may optionally be a base inducednucleophilic addition reaction across the unsaturated (ethylenic) bond,for example a Michael addition or alternatively/additionally aBaylis-Hillman Reaction.

The coating composition is preferably an aqueous-based composition;alternatively a solvent (for example MEK—methyl ethyl ketone—orisopropyl acetate) based system can be used. Organic solvent-basedsystems may optionally be used in combination with polyester binders,and/or aromatic crosslinkers.

The ethylenically unsaturated compound is preferably dispersible ormiscible (as opposed to soluble) in water.

The coating of the present invention may form a layer which covers atleast one face of the substrate listed above. The water-dispersiblepolymer may by way of non-limiting example be selected from waterdispersible acrylates, urethanes, urethane acrylates, styrenebutadiene/maleic anhydride copolymers and mixtures thereof. The waterdispersible polymer forms a smooth, film-formed and ink-receptivesurface.

Acrylic polymers used as the water dispersible polymer include(co)polymers obtained by the free-radical addition polymerization of atleast one (meth)acrylic type monomer and optionally of other vinylic orallylic compounds. The acrylic polymers provide a smooth film-formed andink-receptive surface.

A wide variety of acrylic polymers are able to fulfill this requirement.Suitable acrylic polymers are homopolymers of (meth)acrylic acid oralkyl (meth)acrylate, the alkyl radical having 1 to 10 carbon atom, orcopolymers of two or more of the said (meth)acrylic type monomer andoptionally of other vinylic or allylic compounds.

As stated above, a water dispersible urethane polymer may also suitablybe used. As with the acrylic polymer, it is essential that this urethanepolymer should be able to provide a smooth film-formed and ink-receptivesurface.

A wide variety of urethane polymers are able to fulfill thisrequirement. Suitable urethane polymers are for example the reactionproduct of an isocyanate-terminated polyurethane prepolymer formed byreacting at least an excess of an organic poly isocyanate, an organiccompound containing at least two isocyanate-reactive groups and anisocyanate-reactive compound containing anionic salt functional groups(or acid groups which may be subsequently converted to such anionic saltgroups) or non-ionic groups and an active hydrogen-containing chainextender.

The water dispersible polymer has sufficiently low levels of reactivefunctional groups to limit the cross-link density in order to providesufficient water resistance for finished film properties whilst leavinga surface which is receptive to printing inks, said inks beingUV-curable, water based or solvent based. Preferably there is less than10 weight % of reactive functional groups.

The amount of water dispersible polymer is for example 10 to 98%,preferably 60-95%, more preferably 74-92% in terms of the weight afterdrying of the coating composition.

The surface layer comprises also an ethylenically unsaturated compound.

The ethylenically unsaturated compound is selected to be miscible in thewet stage in the aqueous phase and to be compatible in the dry stagewith the water dispersible polymer itself. Consequently, theethylenically unsaturated compound acts as a plasticiser for the surfacelayer once hardened allowing the easy penetration of the radiationcurable ink thereto. Alternatively, or as well, the ethylenicallyunsaturated compound may be provided as part of the water dispersiblepolymer itself—for example as a functional side chain thereof.

The ethylenically unsaturated compound must also be able, when theprinted film is submitted to radiation in order to cure the ink, toreact with the unsaturated components of the ink which have penetratedinto the surface layer.

This reaction between the ethylenically unsaturated compounds of thesurface layer and the unsaturated compounds of the radiation curable inkforms chemical bonds between those compounds and simultaneouslycrosslinks the surface layer, thereby generating the final resistantproduct.

Preferably, the ethylenically unsaturated compound contains 1 to 10double bonds per molecule and still more preferably 2 to 5 double bondsper molecule (or per functional group in the event that the compound isprovided as a pendant side chain from, or otherwise as part of, thewater dispersible polymer).

Suitable ethylenically unsaturated compounds are the ester derivativesof [alpha], [beta]-ethylenically unsaturated acids, such as acrylic ormethacrylic acids, itaconic or citraconic acids, maleic or fumaricacids, etc. with polyols or alkoxylated polyols. Other suitableethylenically unsaturated compounds include derivatives of isocyanateprepolymers or oligomers reacted with ethylenically unsaturated alcoholsand ethoxylated variants thereof, such as Desmodur (Bayer) trifunctionalisocyanate reacted with hydroxylethyl methacrylate. In other words,ethylenically unsaturated compounds used in accordance with theinvention may contain one or more urethane linkages in addition to, orinstead of, one or more ester linkages.

The suitable polyols include saturated aliphatic diols such as ethyleneglycol, diethylene glycol, triethylene glycol, propylene glycol,dipropylene glycol, tripropylene glycol, butylene glycols, neopentylglycol, 1,3- and 1,4-butane diols, 1,5-pentane diol, 1,6-hexanediol and2-methyl-1,3 propanediol. Glycerol, 1,1,1-trimethylolpropane, bisphenolA and its hydrogenated derivatives may also be used. The suitablealkoxylated polyols include the ethoxylated or propoxylated derivativesof the polyols listed above.

Examples of ethylenically unsaturated compounds which can be usedaccording to the invention are polyfunctional acrylates such asdifunctional acrylates, such as 1,4-butane diol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, triethylene glycoldiacrylate, polyethylene glycol diacrylate, tripropylene glycoldiacrylate, 2,2-dionol diacrylate, bisphenol A diacrylate, etc.,trifunctional acrylates such as pentaerythritol triacrylate,trimethylolpropane triacrylate, etc., tetrafunctional acrylates, etc.

It is to be understood that the methacrylate derivatives correspondingto these acrylate derivatives could also be used.

Moreover, it has been found that polyallyl derivatives such astetraallyloxyethane are also suitable. Suitable materials in thisconnection are commercially available under the trade name EBECRYL® fromCytec Industries Inc.

The amount of the ethylenically unsaturated compound can for example befrom about 2 to about 90% by weight of the acrylic polymer, andpreferably is from about 2 to about 15% or 2 to 10% (in the presentspecification, all percentages are dry weight based).

Suitable cross-linking agents include carbodiimide & aziridinecrosslinkers, and cross-linkers disclosed in for example WO 02/31016.The cross-linkers can form bonds between carboxyl, hydroxyl or aminefunctional groups at the interface between the base and the topcoat.

The crosslinking agent may also improve the hardness and/or waterresistance of the surface layer deposited on the film and consequently,of the finished product, whilst resulting in a surface layer which, oncehardened, allows the easy penetration of the radiation curable inkthereto.

For example, 1-10% of crosslinker may be used, or more preferably 1-5%or 2-5%.

For example, where the polymer is an acrylic polymer, the amount of thecrosslinking agent can be up to 10% by weight of the acrylic polymer,and preferably is from 1 to 5% by weight of the acrylic polymer.

The surface layer can contain all other additional agents, if necessary,for preventing the blocking of one sheet to another, and for improvingthe sheet running property, antistatic property, non-transparencyproperty, etc. These additional agents are generally added in a totalamount not exceeding about 40% by weight of the acrylic polymer. As saidadditional agent, for example, a pigment such as polyethylene oxide,silica, silica gel, clay, talc, diatomaceous earth, calcium carbonate,calcium sulfate, barium sulfate, aluminium silicate, synthetic zeolite,alumina, zinc oxide, titanium oxide, lithopone, satin white, etc. andcationic, anionic and nonionic antistatic agents, etc. may be used.

For example, an ink adhesion promoter and surface hardener may be used,e.g. colloidal silica. An ink adhesion promoter and surface hardener mayfor example be present in an amount of 5 to 20%.

Suitable antiblock materials which may be used include silica, clays,non-film forming polymers (e.g. PMMA dispersions and beads), for examplein an addition amount of 0.1 to 3%, preferably 0.1 to 1.0%.

Water may be used to give coating solids of approximately 5 to 20%.

According to the present invention, the surface layer may be applied asan aqueous dispersion at about 0.5 to about 2.5 g/m² on the substrate bythe method of roll coating, blade coating, spray coating, air knifecoating, rod bar coating, reverse gravure, etc. on the substrate andthen dried, for example, in a hot air oven.

After the drying step, the surface layer comprises thus the waterdispersible polymer, smoothly crosslinked by the crosslinking agent and,included in the acrylic polymer matrix, the ethylenically unsaturatedcompound. This allows the easy penetration of the radiation curable inkinto the surface layer as well as its subsequent reaction with theethylenically unsaturated compound.

The present invention does not use a primer. However, before applyingthe surface layer, if sufficient functionality is not available at thesurface of the substrate, it can optionally be pretreated in aconventional manner with a view to improve wetting & adhesion. For thispurpose, it is possible, for example, to pretreat the substrate by thecorona effect, corona discharge, flame, or oxidizing chemicals, but itshould be understood that all known techniques aiming at improving thesurface of a sheet-like item with a view of the application of acomposition, may be suitable.

A reverse face of the substrate, namely a face not covered by thesurface layer, can be covered with a pressure-sensitive adhesive layerwhich consists of a commonly used pressure-sensitive adhesive agent.Furthermore, if necessary, a releasing film or sheet consisting of areleasing agent, can cover the pressure-sensitive adhesive layer. Thislaminate comprising the printing sheet according to the invention can beused as an adhesive label which may be affixed to most types of surface.In certain embodiments, the reverse face is also covered by a surfacelayer having the same coating composition as the surface layer on theother face. The surface layer on the reverse face comprises no primerlayer.

Another aspect of the invention concerns thus a printable film intendedfor labels comprising a substrate of which only one face is coated witha surface layer and of which the other face is coated with apressure-sensitive adhesive layer which is itself covered with areleasing film or sheet.

Another aspect of the present invention relates to a process for themanufacture of a printable film comprising the step of coating at leastone side of a substrate with an aqueous dispersion comprising a waterdispersible polymer and an ethylenically unsaturated compound and asuitable crosslinking agent and optionally conventional additives, andcomprising further the step of drying the coating so obtained. In oneembodiment, the process further comprises the step of applying an ink tothe dried coating at a time when the coated film has been supplied on toa printing station.

The process of manufacture of a printable film may optionally comprisebefore the step of coating at least one face of the substrate, a furtherpretreatment step of the substrate (such as corona discharge treatment).

In a particular embodiment directed to the preparation of labels, onlyone face of said substrate is coated with a surface layer and the oneface-coated substrate so obtained is coated with a pressure-sensitiveadhesive or in a variant, the pressure-sensitive adhesive may betransferred from a release liner with which the coated substrate iscombined.

Another object of the present inventions concerns a printed filmcomprising a substrate of which at least one face is coated with asurface layer comprising a water dispersible polymer and anethylenically unsaturated compound and suitable crosslinker, said coatedface of the substrate being printed by conventional methods such asoffset printing, gravure, flexography, screen process printing andletterpress printing using radiation curable ink and subsequentlyradiation cured.

Ink formulations for radiation curing contains generally pigments,vehicle, solvent and additives. The solvents in these systems arelow-viscosity monomers, capable of reacting themselves (i.e., used asreactive diluents). The vehicle is usually composed of a resin derivedfrom unsaturated monomers, prepolymers or oligomers such as acrylatesderivatives which are able to react with the ethylenically unsaturatedcompound of the surface layer. For a UV ink, the “additives” contain alarge amount of photoinitiators which respond to the photons of UV lightto start the system reacting.

A UV ink formulation may be generalized as:

Pigment 15-20% Prepolymers 20-35% Vehicle 10-25% Photoinitiators  2-10%other additives  1-5%.

For an electron beam curable ink, the “additives” contain generally nophotoinitiator.

The low viscosity monomers, sometimes termed diluents, are capable ofchemical reactions which result in their becoming fully incorporatedinto the ultimate polymer matrix.

The vehicle provides the “hard resin” portion of the formulation.Typically, these are derived from synthetic resins such as for example,urethanes, epoxides, polyesters which have been modified by reactionwith compounds bearing ethylenic groups such as for instance(meth)acrylic acid, hydroxyethyl(meth)acrylate, reaction product ofcaprolactone with unsaturated compounds bearing a hydroxyl group, andthe like.

Appropriate adjustments could be made in the selection of theprepolymers and monomers used in order to achieve the requiredviscosities for the different methods of application.

Another aspect of the invention relates to a process for the manufactureof a printed film comprising the steps of

a) coating a substrate with an aqueous dispersion comprising a waterdispersible polymer and an ethylenically unsaturated compound and asuitable crosslinker;

b) drying the coating so obtained;

c) inking the dried coating with radiation-curable ink;

d) curing the ink with UV or EB radiations.

It is to be noted that the different steps of this process may beeffected in the same conditions (speed, costs, etc.) as withconventional surface layer.

Finally, the invention concerns also a printed film as obtained byinking a printable film according to the invention, and especially aprinted label so obtained.

An example of a coated film in accordance with the present invention isshown, schematically and not to scale, in FIG. 1.

EXAMPLES

The following Examples are given for the purpose of illustrating thepresent invention and may be coated onto a substrate film in accordancewith standard techniques.

The Raw materials used in these examples are sourced from the followingsuppliers: Cytec Surface Specialties S.A./N.V. Anderlechtstraat, 33,1620 Drogenbos; Alberdingk Boley GmbH Europe Headquarters, DuesseldorferStr. 53, 47829 Krefeld, Germany; Cray Valley Laporte Road,Stallingborough, North East Lincolnshire, DN41 8DR; Xama AziridenesFlevo Chemie (Nederland) B.V., Havendijk 8a, 3846 AD Harderwijk, TheNetherlands; Gasil Silica INEOSSilicas Limited, Warrington, England WA51AB; Baxenden Chemicals Ltd, Paragon Works, Worsley Street, RisingBridge, Accrington, BB5 2SL; Bayer Material Science 100 Bayer Road,Pittsburgh, Pa. 15205; Grace Davison Oak Park Business Centre, AlingtonRoad, Little Barford, St. Neots, Cambs PE19 6WL; NIPPON SHOKUBAI EUROPEN.V. Haven 1053, Nieuwe Wegl, B-2070 Zwijndrecht, Belgium; NissandoIndustries Inc. 1-2-3, Onodai Midori-ku, China; DSM NeoResins+Sluisweg12, PO Box 123 5140 AC Waalwijk, The Netherlands.

Sample 1

Acrylic copolymer (Craymul 8500; Cray Valley) 82.8 (74.0-90.9)% Silica(Gasil HP250; Crossfield)  0.2 (0.1-1.0)% Colloidal silica (Ludox x30;GRACE Davison)   12 (5-20)% EBECRYL ® 160 (Cytec)   3 (2-10)% XAMA-7(polyfunctional aziridene crosslinker;   2 (2-5)% Bayer Polymers) Waterto give coating solids of approximately 5-20%

Sample 2

Acrylic copolymer (Crayrnul 8405; Cray Valley) 81.5 (74.0-90.9)% Silica(Seahostar KE250; Nippon Shokubai)  0.5 (0.1-1.0)% Colloidal silica(Bindzil 15/500; GRACE Davison) 5-20% EBECRYL ® 160 (Cytec)   5 (2-10)%PFAZ 322 (polyfunctional aziridene crosslinker;   3 (2-5)% BayerPolymers) Water to give coating solids of approximately 5-20%

Sample 3

PU Dispersion (Witcobond 315-40; Baxenden 33% Chemicals) Acryliccopolymer (Craymul 8500; Cray Valley) 42.8 (41.0- 57.9)% Silica(Seahostar KE250; Nippon Shokubai)  0.5 (0.1-1.0)% Colloidal silica(Ludox x30; GRACE Davison)   15 (5-20)% EBECRYL ® 160 (Cytec)   5(2-10)% XAMA-2 (polyfunctional aziridene crosslinker;  3.7 (2-5)% BayerPolymers) Water to give coating solids of approximately 5-20%

(The stated ranges in parentheses in the above samples 1 to 3 arepreferred ranges for the stated materials, and the stated numbers beforethe parentheses are specific examples of contemplated formulationswithin the suggested preferred ranges.)

The following more specific formulations in accordance with theinvention were prepared, or prepared in a form suitable for laboratorytesting in the absence of a stated antiblock component, and tested asdescribed:

Example 1

Component Dry % Description Alberdingk U3305 76.96 PU Acrylatedispersion Ludox X30 10.00 Colloidal Silica Antiblock 1.00 ParticulatePMMA Sartomer CN133 7.00 Aliphatic Oligomer Tri-acrylate Dowfax 2A1 0.04Dispersion surfactant CX 100 5.00 Aziridene Cross-linker (DSM)

Example 2

Component Dry % Description Ucecoat 7655 85.00 PU Acrylate from Cytecwith ethylenic unsaturation built on polymer backbone Ludox X30 10.00Colloidal Silica Antiblock 1.00 Particulate PMMA PZ-28 4.00 AzirideneCross-linker (PolyAziridine, LLC)

Example 3

Component Dry % Description Alberdingk U3305 76.96 PU Acrylatedispersion Ludox X30 10.00 Colloidal Silica Antiblock 1.00 ParticulatePMMA Sartomer CN133 7.00 Aliphatic Oligomer Tri-acrylate Dowfax 2A1 0.04Dispersion surfactant Carbodilite E-03A 5.00 Carbodiimmide Cross-linker(Nissindo Industries)

Example 4

Component Dry % Description Ucecoat 7655 64.56 PU Acrylate from Cytecwith ethelenic unsaturation built on polymer backbone Ludox X30 10.00Colloidal Silica (Grace Davidson) Antiblock 1.00 Particulate PMMA CX 1004.00 Aziridene Cross-linker (DSM) R610 20.00 PU Dispersion (DSM)

Example 5

Component Dry % Description Ucecoat 7655 77.96 PU Acrylate from Cytecwith ethelenic unsaturation built on polymer backbone Ludox X30 10.00Colloidal Silica Antiblock 1.00 Particulate PMMA CX 100 4.00 AzirideneCross-linker Sartomer 454 7.00 Ethoxylated TMPTA (Sartomer) Dowfax 2A10.04 Dispersion Surfactant

Other more specific formulations contemplated in accordance with theinvention are as follows:

Example 6

Component Dry % Description Alberdingk U3305 76.96 PU Acrylatedispersion Bindzil 30/310 10.00 Colloidal Silica Antiblock 1.00Particulate PMMA EBECRYL ® 1160 7.00 Ethoxylated TMPTA (Cytec) Dowfax2A1 0.04 Dispersion surfactant CX 100 4.00 Aziridene Cross-linker

Example 7

Component Dry % Description Alberdingk U3305 76.96 PU Acrylatedispersion Bindzil 30/310 10.00 Colloidal Silica Antiblock 1.00Particulate PMMA Sartomer 454 7.00 Ethoxylated TMPTA Dowfax 2A1 0.04Dispersion surfactant Ucarlink XL29SE 5.00 Carbodiimmide Cross-linker(Dow Chemicals)

The systems of these samples and examples should have a usable pot lifeof approximately 8 to 12 hours before crosslinker is consumed.Nevertheless, addition of further crosslinker revitalizes theformulation, without significant effects on the finished filmproperties.

After coating of the above specific formulations of Examples 1 to 5 ontoa film, the coated film was dried in a hot air oven and then printed ina screen printing process with commercially available UV curable screeninks, at 5 to 15 g/m². Examples are RN752 & 650-CWHD inks from FUJIFILMSERICOL, UVSF-172 ink from PARAGON INKS, RSP Series inks from NORCOTE orCombiwhite USW90004 & UVOSCREEN II™ ink from FLINT INKS.

The printed film so obtained was UV cured using typical commercialconditions

UV lamp powers of 100-200 W/cm at typical press speeds of 50-100 m/min.

The printed film finally obtained was tested according to followingmethod:

Exposure to extreme wet conditions at high temperature (typically >90°C.) and low temperature (0° C.) followed by immediate scratch testing.Each of Examples 1 to 5 passed the high temperature test, and Example 3passed a modified low temperature test at 4° C.

Similar results are expected in relation to each of Examples 6 and 7,and specific Examples formulated in accordance with Samples 1 to 3.

The results showed that the new primerless system of the presentinvention delivers an excellent printed film suitable for labeling in,for example, the beverage industry.

1. A primer-less coating composition for facestock, comprising: a binderbeing a water-dispersible polymer comprising a polyurethane acrylate; anethylenically unsaturated compound which is aqueous-dispersible andwhich is provided in the composition as a separate compound and/or whichforms part of and/or is pendant from the backbone of saidwater-dispersible polymer, wherein said ethylenically unsaturatedcompound is able to form a covalent bond with an ink; and a crosslinker,wherein said crosslinker is used to bind functional groups on the filmsurface with functional groups of the coating composition and issuitable for binding and effectively adhering the coating to thefacestock.
 2. The coating composition as claimed in claim 1, whereineffective adhesion is determined using exposure to extreme wetconditions at a high temperature and a low temperature, followed byimmediate scratch testing.
 3. The coating composition as claimed inclaim 2, wherein the high temperature is 90° C. or greater and the lowtemperature is around 0° C.
 4. The coating composition as claimed claim1, wherein the crosslinker interacts with carboxyl, hydroxyl or aminogroups on both the surface of the facestock and the components of thecoating composition.
 5. The coating composition as claimed in claim 1,wherein the crosslinker is present throughout the coating and reachesfrom the facestock where it binds to functional groups thereon, all theway through the topcoat where it crosslinks the polymer and interactschemically with the ethylenically unsaturated compound, to the surfacewhere it locks in the ethylenically unsaturated compound and yet leavesfunctional groups available on the ethylenically unsaturated compound tobind the ink.
 6. The coating composition according to claim 5, whereinthe chemical interaction is a three-way interaction including theethylenically unsaturated compound, the crosslinker and the polymer,thereby effectively forming a pre-polymer on the film surface for thereception of ink and subsequent curing.
 7. The coating composition asclaimed in claim 1, wherein in addition to binding and effectivelyadhering the coating to the facestock, the crosslinker is also effectiveto provide facestock with water resistance.
 8. The coating compositionas claimed in claim 1, wherein the cross-linker is provided in thecomposition in an amount effective for binding and effectively adheringthe coating to the facestock.
 9. The coating composition according toclaim 8, wherein the amount of crosslinker is selected with regard toone or more of: a. the nature of the crosslinker itself; b. the abilityof the crosslinker to hydrolyse; c. the nature of the reaction of thecrosslinker with the ethylenically unsaturated compound; d. the natureof any three way interaction between the crosslinker, the ethylenicallyunsaturated compound and the polymer; e. the functionality of thematerials of the composition, in particular the level of acidfunctionality in the polymer.
 10. The coating composition as claimed inclaim 8, wherein the crosslinker is present in the coating compositionin an amount in excess of that required for stoichiometric crosslinkingof the water dispersible polymer.
 11. The coating composition accordingto claim 1, wherein the crosslinker is present in an amount of from 1 to10% w/w of the composition.
 12. The coating composition according toclaim 11, wherein the crosslinker is present in an amount of from 2 to5% w/w of the composition.
 13. The coating composition as claimed inclaim 1, wherein binding in the finished product occurs between thecrosslinker and the ethylenically unsaturated compound.
 14. The coatingcomposition as claimed in claim 1, which is able to provide asmooth-film formed and ink-receptive surface suitable for printing. 15.The coating composition as claimed in claim 1, wherein saidwater-dispersible polymer is present in an amount of 10 to 98% by weightafter drying of the coating composition.
 16. The coating composition asclaimed in claim 1, wherein said ethylenically unsaturated compound ispresent in an amount of 2 to 90% by weight after drying of the coatingcomposition.
 17. The coating composition as claimed in claim 1, whereinsaid crosslinking agent is selected from a carbodiimide crosslinker, oran aziridine crosslinker.
 18. The coating composition as claimed inclaim 17, wherein a carbodiimide crosslinker is provided in thecomposition in an amount effective to bind and effectively adhere thecoating to the facestock.
 19. The coating composition as claimed inclaim 17, wherein an aziridine crosslinker is provided in thecomposition in an amount effective to bind and effectively adhere thecoating to the facestock.
 20. The coating composition according to claim1, wherein the crosslinker is absent any isocyanate crosslinker.
 21. Thecoating composition according to claim 1, wherein the ethylenicallyunsaturated compound is able to form a covalent bond with an ink byvirtue of ethylenically unsaturated groups extant in the coating at thetime an ink is applied thereto.
 22. A printable film, comprising asubstrate and at least one surface layer formed from the coatingcomposition as claimed in claim 1, comprising no primer layer.
 23. Aprintable film, comprising: a substrate; a first surface layer, suitablefor printing, formed from a coating composition as claimed in claim 1,comprising no primer layer; and a second surface layer, suitable foradhesion.
 24. A printable film, comprising: a substrate; a first surfacelayer; and a second surface layer, suitable for adhesion, wherein thefirst surface layer and the second surface layer are formed from thecoating composition as claimed in claim 1, and wherein the first surfacelayer and the second surface layer comprise no primer layer.
 25. Theprintable film as claimed in claim 22, wherein the substrate is selectedfrom the group consisting of polymer films, polyolefin films, papers,synthetic papers, woven fabrics, nonwoven fabrics, ceramic sheets,metallic fiber sheets, metallized sheets (film), metallic foils,metallic plates, and multilayer composite sheets formed by combinationof said materials.
 26. The printable film as claimed in claim 22,wherein the substrate is an oriented polypropylene film.
 27. Theprintable film as claimed in claim 22, wherein only one face is coatedwith a surface layer and the reverse face of the substrate is coveredwith a pressure-sensitive adhesive layer.
 28. A printed film, comprisingthe printable film as claimed in claim 22, further carrying print.
 29. Aprocess for the manufacture of a printable film, comprising the step of:coating at least one side of a substrate with an aqueous dispersioncomprising the coating of claim 1; and drying the coating so obtained.30. The process for the manufacture of a printed film as claimed inclaim 29, further comprising the steps of: inking the dried coating witha radiation curable ink; and curing the ink with UV or electronic beam(EB) radiations.